The present invention relates generally to the selection of images on a computer screen, and more particularly methods for selecting objects on the screen of a pen-based computer system.
A pen-based computer system is typically a small, hand-held computer where the primary method for inputting data includes a "pen" or stylus. A pen-based computer system is commonly housed in a generally rectangular enclosure, and has a dual-function display assembly providing a viewing screen along one of the planar sides of the enclosure. The dual-function display assembly serves as both an input device and an output device. When operating as an input device, the display assembly senses the position of the tip of a stylus on the viewing screen and provides this positional information to the computer's central processing unit (CPU). Some display assemblies can also sense the pressure of the stylus on the screen to provide further information to the CPU. When operating as an output device, the display assembly presents computer-generated images on the screen.
The dual-function display assemblies of pen-based computer systems permit users to operate the computer as a computerized notepad. For example, graphical images can be input into the pen-based computer by merely moving the stylus on the surface of the screen. As the CPU senses the position and movement of the stylus, it generates a corresponding image on the screen to create the illusion that the stylus is drawing the image directly upon the screen, i.e. that the stylus is "inking" an image on the screen. With suitable recognition software, text and numeric information can also be entered into the pen-based computer system in a similar fashion.
With both pen-based computers and ordinary computers, it is often desirable to select part or all of an "object" displayed on a screen. These objects can take various forms such as text objects, graphical objects, numerical objects, tabular objects, etc. For example, when word processing, it is often desirable to be able to select a word, a sentence, or a paragraph for deletion or for a cut-and-paste operation. With a graphical object, part or all of a graphic can be selected for movement, resizing, or reorientation.
This selection process is often referred to as a "highlighting" process because the selected portion of the object is emphasized in some dramatic fashion such as reverse video, a bolder line, or a distinctive background. With both conventional and pen-based computers, the selection step is usually a predecessor to some form of action to be undertaken with the selected material. The selection process of the prior art tends to be quite literal. For example, if a word is to be selected a pointer in a selection mode is carefully moved over the word or words to cause selection. Alternatively, in mouse and other pointer-type systems, a word can be clicked on twice to indicate that the word should be highlighted, three times to indicate that the word sentence should be highlighted, four times to indicate that the paragraph should be highlighted, etc.
While this literal selection process works well in general purpose computer systems using traditional pointing devices such as mice, track balls, etc., it is not very well adapted to the pen-based computer system environment. Since the primary input device of a pen-based system is a stylus, it is difficult or undesirable to be required to accurately point to the portions of an object to be selected.